Letter to the Editor Response to

The criticisms presented in the preceding letter from Cantù et al. are essentially attributable to a serious misunderstanding of the structural parameters shown by Hirai et al. (1996a). This is evidently derived from some unsuitable expressions in a part of the structural parameters (scattering densities) in the above paper, which should be corrected by Hirai et al. Such corrections of the expressions do not affect the contents of the above paper, since the results in the above paper were derived from concrete scattering data analyses and modeling method. Those corrections can answer all criticisms of Cantù et al. as follows. As shown by Hirai et al. (1996a), our analyses were carried out by using Eq. 6 on the basis of a reasonable model, namely a double-shelled ellipsoid of rotation composed of a shell and a core. Clearly we measured the relative scattering intensities experimentally and used Eq. 6 for a profile fitting of the experimental scattering curve calibrated in relative scale. As is well known for solution small-angle scattering (Stuhrmann and Miller, 1978), only a difference between the average scattering densities of the solute and solvent contributes to effective scattering intensities. This is also evidently shown in Eq. 6 in the above paper (Hirai et al., 1996a), namely, that Eq. 6 contains average excess scattering densities (contrasts) of model components (shell and core), not average scattering densities of them. Therefore , evidently relative values of contrasts have physical meanings and change profiles of model scattering functions obtained by Eq. 6. When we had carried out the shell-modeling analyses, we had given the average scattering density of the solvent to be 1, which does not mean the normalization of scattering density by that of the solvent owing to the above reason. If we subtract 1 from the values of the scattering densities shown in the paper, the relative values of contrasts can be obtained. The alternation of the expression from the average scattering densities to the contrasts should be done by Hirai et al., since this change does not affect other structural parameters and results obtained from the optimized models, which is ensured by the expression of Eq. 6. In addition, we showed very well agreements of the simulated scattering curves with the experimental ones by using our prolate double-shelled ellipsoid models, not by using a hard sphere or a hard ellipsoid, which have also clearly shown in our other papers …